sin2A-sin2B=2sincos是怎么出来的
答案:1 悬赏:60
解决时间 2021-01-19 19:03
- 提问者网友:几叶到寒
- 2021-01-18 18:53
sin2A-sin2B=2sincos是怎么出来的
最佳答案
- 二级知识专家网友:酒者煙囻
- 2021-01-18 19:31
sin(x+y)=sinx.cosy + cosx.siny(1)
sin(x-y)=sinx.cosy - cosx.siny(2)
(1)-(2)
sin(x+y)-sin(x-y) = 2cosx.siny
2A=x+y (3)
2B=x-y (4)
(3)+(4)
x=A+B
(3)-(4)
y=A-B
sin(x+y)-sin(x-y) = 2cosx.siny
sin2A -sin2B = 2cos(A+B).cos(A-B)
sin(x-y)=sinx.cosy - cosx.siny(2)
(1)-(2)
sin(x+y)-sin(x-y) = 2cosx.siny
2A=x+y (3)
2B=x-y (4)
(3)+(4)
x=A+B
(3)-(4)
y=A-B
sin(x+y)-sin(x-y) = 2cosx.siny
sin2A -sin2B = 2cos(A+B).cos(A-B)
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